L'Oreal's push into China's $US32 billion (NZ$41 billion) beauty market has a hidden cost - if you're a rabbit or a mouse.

The Paris-based maker of shampoos and lipsticks this month agreed to pay $US843 million for Chinese cosmetics face-mask maker Magic Holdings International, accelerating expansion into the world's second-biggest economy, where it derived about 6 per cent of sales last year.

While L'Oreal is barred by European Union rules from testing on animals within the EU, China's government requires such trials for every new beauty product.

China is the only major market where companies must test their mascaras and lotions on animals. Rabbits are killed or ingredients dripped into their eyes during tests, London animal rights group Cruelty Free International says.

China's policies create a problem for companies such as L'Oreal and Procter & Gamble that want to sell in the country without alienating consumers in markets that demand humane treatment of animals.

India banned animal testing for beauty products last month. The EU, which has long barred such trials within its borders, tightened regulations this year to also prohibit products tested on animals elsewhere.

It would be against European rules to sell any product that has been tested on animals in China, so companies would need to reformulate their wares for the two markets.

In China, companies are required to submit samples of their products to be used for tests at local laboratories, according to People for the Ethical Treatment of Animals. PETA estimates at least 72 animals are used for each product.

Market researcher Mintel says at least 4249 beauty products were introduced in China over the past year. That would translate into more than 300,000 animals used in tests, according to Bloomberg calculations based on the estimates.

L'Oreal says less than 1 per cent of its total safety tests on cosmetics ingredients involve animals. Procter & Gamble, the largest seller of beauty products in China, said it did not test on animals unless required by law.

In June, Xu Jingquan, secretary-general at the All-China Federation of Industry and Commerce, Beautyculture and Cosmetics Chamber said: ''Our R&D isn't as sophisticated, and the consumer here doesn't think as much about ideals such as animal testing. They care about the price, the brand and the product.''